1. Field of the Invention
The present invention relates to a focused ion beam apparatus configured to process a sample with a focused ion beam, a sample processing method using the same, and a computer program for focused ion beam processing.
2. Description of the Related Art
In the related art, the focused ion beam apparatus has been used for etching a semiconductor device, for example, and obtaining a cross section for observation, or for slicing the sample into a thin piece and fabricating a sample piece for a transmission electron microscope (Japanese Patent No. 2973211). In recent years, there arise needs for processing the sample into complex shapes such as a lens shape or a solder ball shape using the focused ion beam apparatus.
The processing with the focused ion beam is performed by specifying a portion to be irradiated with the focused ion beam (processing area) by a pointing device or the like on a sample image (JP-A-2008-270025).
In contrast, in order to process the complex shapes having curved lines or curved surfaces efficiently by the focused ion beam, it is necessary to set the processing area into an arbitrary shape instead of simple linear shapes or rectangular shapes.
Therefore, a method of storing image data (bitmap data) of various shapes in a control unit of the focused ion beam apparatus in advance, specifying desired image data as the processing area, and irradiating with a beam along the complex shape of the image data is employed.
This technique allows processing of the complex shapes along the image data by reading pixel coordinates included in the image data specified on a sample image (processing area) on the control side, and irradiating each pixel with the focused ion beam.
When setting the processing area on the basis of the image data and irradiating the same with the beam, there is a case in which scaling (deformation) of the processing area is desired. For example, when an upper half of the processing area has a protruding shape and a lower half of the same has a substantially flat shape, if only the protruded upper half can be etched intensively in a stage after a predetermined processing is proceeded, the processing speed or the processing efficiency is improved. Also, by changing the size of the processing area in the course of processing, etching pits having different diameters in the direction vertical to the direction of irradiation of the beam are obtained.
However, when the image data including the pixels are reduced in scale on the sample image, the number of pixels is reduced according to the ratio of scale reduction of the image data, and hence the image data is deteriorated in finesse of resolution. In this case, since the position to be irradiated with the focused ion beam is reduced, the processing area of the image data after reduction in scale cannot reproduce the shape of original image data. When the image data is enlarged in scale, the number of pixels is increased, but the image may be deteriorated and the shape of the original image data cannot be reproduced unless intensities of the pixels are set adequately.